An exhaust system, in which reducing agent is introduced into the exhaust gas stream through a reactant release arrangement to reduce the pollutant emission, is known from DE 10 2006 059 507 A1. Highly efficient mixing of the reactant with the exhaust gas can be achieved in this prior-art arrangement by the reactant being introduced in a direction into the exhaust gas stream that is directed essentially opposite a main direction of flow of the exhaust gas stream in the area in which the reactant is introduced.
One problem arising in connection with the introduction of reagents, e.g., urea or a urea-water mixture, is that deposits may develop due to reactant precipitating on a wall of the exhaust gas canal carrying the exhaust gas stream. Such deposits are especially critical especially if they occur in the area of the reactant release arrangement which is generally also called injector, because there is a risk, on the one hand, that the correct quantity of reactant cannot be released any longer, and, on the other hand, the direction of propagation of the released reactant may be compromised as well. Depending also on the geometric configuration of the area in which the reactant is released, recirculation zones may develop, in which reactant released in a droplet or spray configuration is recirculated from the reactant release arrangement and can precipitate very close to the area of release, i.e., for example, the tip of an injector. The risk of recirculation is especially great if, as is known from DE 10 2006 059 507 A1, the exhaust gas stream moves the reactant introduced opposite its direction of flow back in the direction of the injector.